1. Field of the Invention
The present invention relates to an anti-BMP9 (Bone morphogenetic protein-9) monoclonal antibody or an antibody fragment thereof binding to human BMP9, a hybridoma producing the antibody or the antibody fragment, a DNA encoding the antibody or the antibody fragment, a vector containing the DNA, a transformant obtained by introduction of the vector, a method for preparing the antibody or the antibody fragment using the hybridoma or the transformant, and a therapeutic agent including the antibody or the antibody fragment as an active ingredient.
Further, the present invention relates to a pharmaceutical composition comprising the antibody or the antibody fragment as an active ingredient for the treatment of anemia such as renal anemia, cancer anemia or the like, and a method for treating anemia such as renal anemia, cancer anemia or the like using the composition.
2. Brief Description of the Background Art
BMP9 is an abbreviation for bone morphogenetic protein 9, and also called GDF2. BMP9 belongs to a BMP (Bone morphogenetic protein) family molecule composed of approximately 20 members, and human BMP9 is a secretory protein composed of 429 amino acids (Non-Patent Document 1).
It is know that BMP9 is mainly expressed in the spinal cord or septum in the fetal stage and in the liver in the adult stage (Non-Patent Documents 2, 3, and 4) and that human BMP9 is a blood circulation factor present in the blood at a concentration of 2-12 ng/mL (Non-Patent Document 5).
Until now, there have been no reports on in vivo functions of BMP9 based on BMP9-deficient mice or administration of anti-BMP9 antibody to animals, but a few reports have been made based on the findings of in vitro studies. Such report includes, for example, a promoting action on generation of hypertrophic chondrocytes or chondrogenic differentiation from mesenchymal cells (Non-Patent Documents 6, 7, and 8), or a promoting action on production or colony formation of blood progenitor cells (Non-Patent Document 9). From these reports, however, it was very difficult to predict that anti-BMP9 antibody has the erythropoietic action in vivo.
Further, a monoclonal antibody having a BMP9-neutralizing activity has been commercialized as an anti-BMP9 monoclonal antibody by R&D systems (Clone No. 360107), but no other antibodies have been known.
Anemia refers to “a condition of having a reduction in the number of erythrocytes, the hemoglobin concentration, and the hematocrit value per unit volume of blood, compared to normal condition (Non-Patent Document 10). There are many factors involved in the control of erythropoiesis, but erythropoietin is the most important and specific factor (hereinafter, referred to as EPO).
EPO promotes proliferation and differentiation of late-stage colony-forming unit-erythroid (CFU-E), and consequently, increases erythrocyte production in vivo (Non-Patent Document 10). EPO is a glycoprotein hormone that is composed of 165 amino acids and has a molecular weight of 30 kDa, and is mainly produced in the kidney (Non-Patent Document 10).
Anemia accompanied by kidney disease (renal anemia) is the most frequent complication of chronic kidney disease (CKD), characterized in that reduced EPO production and reduced number of erythrocytes result from failure of the EPO-producing tissue, kidney (Non-Patent Document 11). It is known that renal anemia affects development and progression of cardiovascular disease, and progression of renal dysfunction, as well as QOL (Non-Patent Documents 11 and 12).
A recombinant human erythropoietin that is a therapeutic agent for renal anemia and a second-generation EPO agent which has been recently developed to have a long blood half-life are generally called ESA (erythropoiesis-stimulating agent) (Non-Patent Document 13).
ESA has a strong erythropoietic action. In some cases, however, ESA administration does not show a satisfactory anemia-improving effect in 15-20% of dialysis patients with renal failure (which called ESA-resistant anemia or ESA-hyporesponsive anemia) (Non-Patent Document 13).
The results of large-scale intervention trials (CREATE and CHOIR studies) show that excessive administration of ESA to patients with ESA resistance causes a poor life prognosis (Non-Patent Documents 11, 12, and 13). Under this background, a significant issue for renal anemia treatment is to overcome ESA resistance, and there is a strong demand to develop a new erythropoiesis-stimulating agent having a different mechanism from EPO.
Meanwhile, anemia accompanied by malignant tumor (cancer anemia) is a symptom observed in many cancers, and caused by two factors: one is associated with disease progression including blood loss and the other relates to chemotherapy or radiotherapy (Non-Patent Document 14).
ESA is known to be effective in cancer anemia, but concerns about a possibility of promoting tumor progression or thrombotic infarction by ESA treatment are pointed out (Non-Patent Document 14). With respect to cancer anemia, therefore, there is also a demand to develop a new erythropoiesis-stimulating agent having a different mechanism from EPO.
As described above, it is required to develop an erythropoiesis-stimulating agent having a different mechanism from EPO for the treatment of renal anemia and cancer anemia. Also, the efficacy and strength of the drug must be considered. Specifically, Japanese criteria for starting administration of ESA is that in case of dialysis patients, the hemoglobin concentration is less than 10 g/dL and the drug should have the efficacy of controlling the hemoglobin concentration between 10-11 g/dL; and that in case of patients with predialysis chronic kidney disease, the hemoglobin concentration is less than 11 g/dL for starting administration of ESA and the drug should have the efficacy of controlling the hemoglobin concentration between 11-13 g/dL (Non-Patent Document 15).
In other words, new erythropoiesis-stimulating agents are required to have two characteristics: efficacy of increasing the hemoglobin concentration by at least 1-2 g/dL and EPO-independency.